Inspired by the cubic Mn CaO cluster of natural oxygen-evolving complex in Photosystem II, tetrametallic molecular water oxidation catalysts, especially M O cubane-like clusters (M=transition metals), have aroused great interest in developing highly active and robust catalysts for water oxidation. Among these M O clusters, however, copper-based molecular catalysts are poorly understood. Now, bio-inspired Cu O cubanes are presented as effective molecular catalysts for electrocatalytic water oxidation in aqueous solution (pH 12). The exceptional catalytic activity is manifested with a turnover frequency (TOF) of 267 s for [(L -Cu) ] at 1.70 V and 105 s for [(L -Cu) ] at 1.56 V. Electrochemical and spectroscopic study revealed a successive two-electron transfer process in the Cu O cubanes to form high-valent Cu and Cu O intermediates during the catalysis.
Herein we report a general electrochemical strategy for the Sandmeyer reaction.
Organic semiconductors for spin-based devices require long spin relaxation times. Understanding their spin relaxation mechanisms is critical to organic spintronic devices and applications for quantum information processing. However, reports on the spin relaxation mechanisms of organic conjugated molecules are rare and the research methods are also limited. Herein, we study the molecular design and spin relaxation mechanisms by systematically varying the structure of a conjugated radical. We found that solid-state relaxation times of organic materials are largely different from that in solution state. We demonstrate that substitution of a lower gyromagnetic ratio nucleus (e. g. D, Cl) on the para-position of the aryl rings in the triphenylmethyl (TM) radical can significantly improve their coherence times (T ). Flexible thin films based on such radicals exhibit ultra-long spin-lattice relaxation times (T ) up to 35.6(6) μs and T up to 1.08(4) μs under ambient conditions, which are among the longest values in films. More importantly, using the TM radical derivative (5CM), we observed room-temperature quantum coherence and Rabi cycles in thin film for the first time, suggesting that organic conjugated radicals have great potentials for spin-based information processing.
Inspired by the cubic Mn 4 CaO 5 cluster of natural oxygen-evolving complex in Photosystem II, tetrametallic molecular water oxidation catalysts,e specially M 4 O 4 cubanelike clusters (M = transition metals), have aroused great interest in developing highly active and robust catalysts for water oxidation. Among these M 4 O 4 clusters,however,copperbased molecular catalysts are poorly understood. Now,b ioinspired Cu 4 O 4 cubanes are presented as effective molecular catalysts for electrocatalytic water oxidation in aqueous solution (pH 12). The exceptional catalytic activity is manifested with at urnover frequency (TOF) of 267 s À1 for [(L Gly -Cu) 4 ]at1.70 Vand 105 s À1 for [(L Glu -Cu) 4 ]at1.56 V. Electrochemical and spectroscopic study revealed as uccessive twoelectron transfer process in the Cu 4 O 4 cubanes to form highvalent Cu III and Cu III OC intermediates during the catalysis.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.
Supercritical fluid ͑SCF͒ technology was proposed to improve the dielectric properties of electron-gun evaporated aluminum oxide ͑AlO x ͒ film in this work. The leakage current of AlO x film deposited at room temperature was suppressed significantly from 10 −4 to 10 −10 A at a bias voltage of −20 V after the SCF treatment mixed with water and propyl alcohol. The evolution of the leakage conduction mechanism was confirmed theoretically from trap-assisted quantum tunneling to the Schottky emission process due to the reduction of electric traps in the AlO x dielectric film. In addition, our work demonstrated the application of SCF-treated AlO x gate dielectric to a pentacene-based thin-film transistor.Organic thin-film transistors ͑OTFTs͒ have been extensively studied and developed for application in electronic devices, such as liquid-crystal display panels and active matrix organic light emitting diodes, because of their excellent hole mobility, low cost, and low fabrication temperature. 1-3 However, the high operating voltage is a serious issue for the conventional OTFT. 4 A high operating voltage not only causes high power consumption but also impacts the reliability of organic materials. In order to obtain low operating voltage and low subthreshold swing ͑SS͒, high-dielectric-constant ͑high-k͒ materials such as HfO 2 , Al 2 O 3 , and Ta 2 O 5 have been proposed as the gate dielectrics of OTFTs to induce a larger number of carriers at lower gate voltages. [5][6][7] In recent years, the fabrication processes of OTFT devices tended to be implemented at low temperatures of 80-200°C for compatibility with plastic substrates. Because electron-gun ͑E-gun͒ evaporation technology offers less surface damage than sputter deposition, E-gun deposited gate dielectrics should be expected to be relatively suitable and compatible with the fabrication of OTFTs. However, low-temperature-deposited ͑LT-deposited͒ dielectrics generally have inferior electrical behaviors and larger leakage current due to the existence of numerous electrical traps. Therefore, it is critical to develop low-temperature posttreatments to terminate the traps in the LT-deposited dielectric film and achieve superior device electrical characteristics. High-pressure H 2 O vapor has been introduced as an appropriate method for terminating traps, 8,9 but a high-temperature environment is also required to bring the high-pressure H 2 O vapor. In the present study, we apply a supercritical CO 2 ͑SCCO 2 ͒ process to passivate the traps in the E-gun deposited AlO x film. The SCCO 2 fluids have liquidlike, gaslike, and high-pressure properties and are thereby able to transport the oxidant ͑H 2 O molecule͒ effectively into the thin dielectric film at low temperatures. 10,11 The effects of SCCO 2 treatment on dielectric characteristics of the E-gun evaporated AlO x film are studied first in this work. Furthermore, the application of SCCO 2 -treated AlO x gate dielectric is performed on the pentacene-based OTFT and compared to the counterpart with SiN x gate dielectric d...
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